Patent GB-904774-A (GB)
Title: Improvements relating to radiation barriers
IPC: G21F3/02
Filed: 1960-07-05
Abstract: Material protective against alpha and beta particles and gamma- and X-rays is made by mixing finely divided heavy metal with a resin dispersion comprising a liquid dispersant, finely divided resin particles, and a gelling agent, and shaping and curing the mixture. The gelling agent is such as to impart thixotropic characteristics to the resin dispersion which has a high initial viscosity so that it can suspend the heavy metal particles, but a lower viscosity when subjected to shear so that it may be shaped.  The resin used in the examples is a mixture of polyvinyl chlorides of different particle sizes.  Mixtures of plasticizers having nearly equal surface tensions may be used as the liquid dispersant; a list of suitable plasticizers is given, those used in the examples being di-2-ethyl hexyl phthalate, di-isodecyl phthalate, octyl fatty phthalic acid esters, dicapryl phthalate, tricresyl phosphate, polyester plasticizer, polyethylene glycol mono-oleate, modified polypropylene glycol dibenzoate, and tertiary butyl perbenzoate.  The gelling agent is preferably dimethyl dioctadecyl ammonium bentonite, others mentioned being silicon dioxide, aluminium stearate, sodium stearate, and fine calcium carbonate coated with a stearate.  A monomer or prepolymer may be included in the resin dispersion; in the examples, 3,9-divinyl spirobi (meta dioxane), 2-ethyl hexyl acrylate and a methacrylate diester of liquid polyethylene are used, but a list of other monomers is given.  Maleic or crotonic acid may be added as a cross-linking agent, and hydroquinone or its methyl ether to inhibit polymerization at room temperature. Lead is normally used as the heavy metal, but reference is also made to iron, steel, silver, gold, and platinum. The heavy metal may comprise 75-95% by weight of the dispersion. Both the resin particles and the lead particles may be made up of two portions, each having a different size range.  The resin dispersion is deaerated under vacuum, mixed with the lead particles also under vacuum, formed into an article, film, or material by dipping, spraying, or brushing, and then cured at 275 DEG -450 DEG F.  In a method of making protective gloves, a preheated form in the shape of a hand is dipped into the resin dispersion and then into a heated liquid to gel the dispersion; after washing with water, the process is repeated until the required thickness of protective material has been built up.  Suitable heating agents are glycerine, ethylene glycol, mineral oils, and molten water-soluble wax.  Other covering materials or clothing, such as jackets and aprons, may also be made.ALSO:Material protective against alpha and beta particles and gamma- and X-rays is made by mixing finely divided heavy metal with a resin dispersion comprising a liquid dispersant, finely divided resin particles, and a gelling agent, and shaping and curing the mixture. The gelling agent is such as to impart thixotropic characteristics to the resin dispersion which has a high initial viscosity so that it can suspend the heavy metal particles, but a lower viscosity when subjected to shear so that it may be shaped.  The resin used in the examples is polyvinyl chloride, but reference is also made to ethyl cellulose, cellulose acetate, and the acrylates.  Mixtures of plasticizers having nearly equal surface tensions may be used as the liquid dispersant.  The gelling agent is preferably dimethyl dioctadecyl ammonium bentonite, others mentioned being silicon dioxide, aluminium stearate, sodium stearate, and fine calcium carbonate coated with a stearate.  A monomer or prepolymer may be included in the resin dispersion.  Lead is normally used as the heavy metal, but reference is also made to iron, steel, silver, gold, and platinum.  The heavy metal may comprise 75-95% by weight of the dispersion.  Both the resin particles and the lead particles may be made up of two portions, each having a different size range.  The resin dispersion is deaerated under vacuum, mixed with the lead particles also under vacuum, formed into an article, film, or material by dipping, spraying, or brushing, and then cured at 275-450 DEG F.  In a method of making protective gloves, a preheated form in the shape of a hand is dipped into the resin dispersion and then into a heated liquid to gel the dispersion; after washing with water, the process is repeated until the required thickness of protective material has been built up. Suitable heating agents are glycerine, ethylene glycol, mineral oils, and molten water-soluble wax.  Other covering materials or clothing, such as jackets and aprons, may also be made.